内容偏移保持不变

Question

我的应用中有一个UIPageViewController，设置如下：

self.pageViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"MainPageViewController"];
self.pageViewController.dataSource = self;
self.pageViewController.delegate = self;
self.pageViewController.view.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
[self addChildViewController:self.pageViewController];
[self.view addSubview:self.pageViewController.view];
[self.pageViewController didMoveToParentViewController:self];

我已使我的 UIViewController 符合 UIScrollViewDelegate 并添加此代码以将 scrollView 委托设置为 self：

    for (UIView *currentView in self.pageViewController.view.subviews) {
    if ([currentView isKindOfClass:[UIScrollView class]]) {
        UIScrollView *scrollView = (UIScrollView *)currentView;
        scrollView.delegate = self;
        break;
    }
}

然后我尝试使用此方法查找当前页面，尽管每当我滚动UIPageViewController 时contentOffset 保持不变：

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
CGFloat pageWidth = scrollView.frame.size.width;
NSInteger page = scrollView.contentOffset.x / pageWidth;

NSLog(@"Content offset.x: %.f", scrollView.contentOffset.x);
}

这是为什么？

Answer 1

我使用UIPageViewController 的委托方法而不是滚动视图使其工作。这是我的解决方案：

-(void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray<UIViewController *> *)previousViewControllers transitionCompleted:(BOOL)completed
{
    if (completed) {
        NSInteger currentIndex = [self.navViewControllers indexOfObject:pageViewController.viewControllers[0]];
    }
}